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  • 1
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    Equilibrium Climate Sensitivity Estimated by Equilibrating Climate Models (2021)
    Details
    Publication Date: 2021-10-12
    Description: The methods to quantify equilibrium climate sensitivity are still debated. We collect millennial-length simulations of coupled climate models and show that the global mean equilibrium warming is higher than those obtained using extrapolation methods from shorter simulations. Specifically, 27 simulations with 15 climate models forced with a range of CO2 concentrations show a median 17% larger equilibrium warming than estimated from the first 150 years of the simulations. The spatial patterns of radiative feedbacks change continuously, in most regions reducing their tendency to stabilizing the climate. In the equatorial Pacific, however, feedbacks become more stabilizing with time. The global feedback evolution is initially dominated by the tropics, with eventual substantial contributions from the mid-latitudes. Time-dependent feedbacks underscore the need of a measure of climate sensitivity that accounts for the degree of equilibration, so that models, observations, and paleo proxies can be adequately compared and aggregated to estimate future warming.
    Keywords: 551.6 ; equilibrium climate sensitivity ; climate models
    Language: English
    Type: map
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    CITATION GEO-LEO
  • 2
    Electronic Resource
    Electronic Resource
    How uncertainties in future climate change predictions translate into future terrestrial carbon fluxes (2005)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 11 (2005), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: We forced a global terrestrial carbon cycle model by climate fields of 14 ocean and atmosphere general circulation models (OAGCMs) to simulate the response of terrestrial carbon pools and fluxes to climate change over the next century. These models participated in the second phase of the Coupled Model Intercomparison Project (CMIP2), where a 1% per year increase of atmospheric CO2 was prescribed. We obtain a reduction in net land uptake because of climate change ranging between 1.4 and 5.7 Gt C yr−1 at the time of atmospheric CO2 doubling. Such a reduction in terrestrial carbon sinks is largely dominated by the response of tropical ecosystems, where soil water stress occurs. The uncertainty in the simulated land carbon cycle response is the consequence of discrepancies in land temperature and precipitation changes simulated by the OAGCMs. We use a statistical approach to assess the coherence of the land carbon fluxes response to climate change. The biospheric carbon fluxes and pools changes have a coherent response in the tropics, in the Mediterranean region and in high latitudes of the Northern Hemisphere. This is because of a good coherence of soil water content change in the first two regions and of temperature change in the high latitudes of the Northern Hemisphere.Then we evaluate the carbon uptake uncertainties to the assumptions on plant productivity sensitivity to atmospheric CO2 and on decomposition rate sensitivity to temperature. We show that these uncertainties are on the same order of magnitude than the uncertainty because of climate change. Finally, we find that the OAGCMs having the largest climate sensitivities to CO2 are the ones with the largest soil drying in the tropics, and therefore with the largest reduction of carbon uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2005.00957.x
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    Paper (German National Licenses)
    Fulltext
  • 3
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    Ten years of wind speed observation on a 45-m tower at Dome C, East Antarctic plateau (2021)
    PANGAEA
    Details
    Publication Date: 2023-03-01
    Description: Long-term, continuous in situ observations of the near-surface atmospheric boundary layer are critical for many weather and climate applications. Although there is a proliferation of surface stations globally, especially in and around populous areas, there are notably fewer tall meteorological towers with multiple instrumented levels. This is particularly true in remote and extreme environments such as the Eastern Antarctic plateau. In the article, we present and analyze 10 years (2010-2019) of data from 6 levels of meteorological instrumentation mounted on a 45-m tower located at Dome C, East Antarctica near the Concordia research station, producing a unique climatology of the near-surface environment. Large seasonal differences are evident in the monthly mean temperature and wind data, depending on the presence or absence of solar surface forcing. Strong vertical temperature gradients (inversions) frequently develop in calm, winter conditions, while vertical convective mixing occurs in the summer leading to near-uniform temperatures along the tower. Seasonal variation in wind speed is much less notable at this location than the temperature variation as the winds are less influenced by the solar cycle; there are no katabatic winds as Dome C is quite flat. Harmonic analysis confirms that most of the energy in the power spectrum is at diurnal, annual and semi-annual scales. Analysis of observational uncertainty and comparison to reanalysis data from ERA-5 indicate that wind speed is particularly difficult to measure at this location.
    Keywords: Antarctic Plateau; Antartic field data for CALibration and VAlidation of meteorological and climate models and satellite retrievals, Antarctic Coast to Dome C; boundary layer; CALVA; Date/Time local; DOME_C_CALVA; Dome C, Antarctica; meteorology; Profile; Temperature; Tower; Weather station/meteorological observation; wind; Wind monitor, R.M. Young, model 05103; Wind speed; WST
    Type: Dataset
    Format: text/tab-separated-values, 911449 data points
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    DATA PANGAEA
  • 4
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    Ten years of shielded ventilated atmospheric temperature observation on a 45-m tower at Dome C, East Antarctic plateau (2021)
    PANGAEA
    Details
    Publication Date: 2023-03-01
    Description: Long-term, continuous in situ observations of the near-surface atmospheric boundary layer are critical for many weather and climate applications. Although there is a proliferation of surface stations globally, especially in and around populous areas, there are notably fewer tall meteorological towers with multiple instrumented levels. This is particularly true in remote and extreme environments such as the Eastern Antarctic plateau. In the article, we present and analyze 10 years (2010-2019) of data from 6 levels of meteorological instrumentation mounted on a 45-m tower located at Dome C, East Antarctica near the Concordia research station, producing a unique climatology of the near-surface environment. Large seasonal differences are evident in the monthly mean temperature and wind data, depending on the presence or absence of solar surface forcing. Strong vertical temperature gradients (inversions) frequently develop in calm, winter conditions, while vertical convective mixing occurs in the summer leading to near-uniform temperatures along the tower. Seasonal variation in wind speed is much less notable at this location than the temperature variation as the winds are less influenced by the solar cycle; there are no katabatic winds as Dome C is quite flat. Harmonic analysis confirms that most of the energy in the power spectrum is at diurnal, annual and semi-annual scales. Analysis of observational uncertainty and comparison to reanalysis data from ERA-5 indicate that wind speed is particularly difficult to measure at this location.
    Keywords: Antarctic Plateau; Antartic field data for CALibration and VAlidation of meteorological and climate models and satellite retrievals, Antarctic Coast to Dome C; boundary layer; CALVA; Date/Time local; DOME_C_CALVA; Dome C, Antarctica; meteorology; Profile; Temperature; Temperature, air; Thermometer/Hygrometer, Vaisala, HMP155, PT100 sensor; Tower; Weather station/meteorological observation; wind; WST
    Type: Dataset
    Format: text/tab-separated-values, 1199618 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 5
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    Effective radiative forcing and adjustments in CMIP6 models (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-01-04
    Description: The effective radiative forcing, which includes the instantaneous forcing plus adjustments from the atmosphere and surface, has emerged as the key metric of evaluating human and natural influence on the climate. We evaluate effective radiative forcing and adjustments in 17 contemporary climate models that are participating in the Coupled Model Intercomparison Project (CMIP6) and have contributed to the Radiative Forcing Model Intercomparison Project (RFMIP). Present-day (2014) global-mean anthropogenic forcing relative to pre-industrial (1850) levels from climate models stands at 2.00 (±0.23) W m−2, comprised of 1.81 (±0.09) W m−2 from CO2, 1.08 (± 0.21) W m−2 from other well-mixed greenhouse gases, −1.01 (± 0.23) W m−2 from aerosols and −0.09 (±0.13) W m−2 from land use change. Quoted uncertainties are 1 standard deviation across model best estimates, and 90 % confidence in the reported forcings, due to internal variability, is typically within 0.1 W m−2. The majority of the remaining 0.21 W m−2 is likely to be from ozone. In most cases, the largest contributors to the spread in effective radiative forcing (ERF) is from the instantaneous radiative forcing (IRF) and from cloud responses, particularly aerosol–cloud interactions to aerosol forcing. As determined in previous studies, cancellation of tropospheric and surface adjustments means that the stratospherically adjusted radiative forcing is approximately equal to ERF for greenhouse gas forcing but not for aerosols, and consequentially, not for the anthropogenic total. The spread of aerosol forcing ranges from −0.63 to −1.37 W m−2, exhibiting a less negative mean and narrower range compared to 10 CMIP5 models. The spread in 4×CO2 forcing has also narrowed in CMIP6 compared to 13 CMIP5 models. Aerosol forcing is uncorrelated with climate sensitivity. Therefore, there is no evidence to suggest that the increasing spread in climate sensitivity in CMIP6 models, particularly related to high-sensitivity models, is a consequence of a stronger negative present-day aerosol forcing and little evidence that modelling groups are systematically tuning climate sensitivity or aerosol forcing to recreate observed historical warming.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Historical Changes and Reasons for Model Differences in Anthropogenic Aerosol Forcing in CMIP6 (2023)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: The Radiative Forcing Model Intercomparison Project (RFMIP) allows estimates of effective radiative forcing (ERF) in the Coupled Model Intercomparison Project phase six (CMIP6). We analyze the RFMIP output, including the new experiments from models that use the same parameterization for anthropogenic aerosols (RFMIP-SpAer), to characterize and better understand model differences in aerosol ERF. We find little changes in the aerosol ERF for 1970–2014 in the CMIP6 multi-model mean, which implies greenhouse gases primarily explain the positive trend in the total anthropogenic ERF. Cloud-mediated effects dominate the present-day aerosol ERF in most models. The results highlight a regional increase in marine cloudiness due to aerosols, despite suppressed cloud lifetime effects in that RFMIP-SpAer experiment. Negative cloud-mediated effects mask positive direct effects in many models, which arise from strong anthropogenic aerosol absorption. The findings suggest opportunities to better constrain simulated ERF by revisiting the optical properties and long-range transport of aerosols. Key Points: - Coupled Model Intercomparison Project phase six (CMIP6) averaged trend in aerosol effective radiative forcing (ERF) is small for 1970–2014 and weakly positive for 2000–2014 - Positive direct aerosol radiative effects in CMIP6 models are associated with strong aerosol absorption - Diverse and often strong cloud-mediated effects primarily determine the magnitude of aerosol ERF in CMIP6
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    CGILS: Results from the first phase of an international project to understand the physical mechanisms of low cloud feedbacks in single column models (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2013-11-12
    Description: ABSTRACT CGILS – the CFMIP-GASS Intercomparison of Large Eddy Models (LESs) and Single Column Models (SCMs) – investigates the mechanisms of cloud feedback in SCMs and LESs under idealized climate change perturbation. This paper describes the CGILS results from 15 SCMs and eight LES models. Three cloud regimes over the subtropical oceans are studied: shallow cumulus, stratocumulus, and well-mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated negative cloud feedbacks, while models with active shallow convection generally simulated positive cloud feedbacks. In the shallow cumulus regime, this relationship is less clear, likely due to the changes in cloud depth, lateral mixing, and precipitation or a combination of them. The majority of LES models simulated negative cloud feedback in the well-mixed coastal stratus/stratocumulus regime, and positive feedback in the shallow cumulus and stratocumulus regime. A general framework is provided to interpret SCM results: In a warmer climate, the moistening rate of the cloudy layer associated with the surface-based turbulence parameterization is enhanced; together with weaker large-scale subsidence, it causes negative cloud feedback. In contrast, in the warmer climate, the drying rate associated with the shallow convection scheme is enhanced. This causes positive cloud feedback. These mechanisms are summarized as “NESTS-SCOPE” (Negative feedback from Surface Turbulence under weaker Subsidence– Shallow Convection PositivE feedback) with the net cloud feedback depending on how the two opposing effects counteract each other. The LES results are consistent with these interpretations.
    Electronic ISSN: 1942-2466
    Topics: Geography , Geosciences
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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    PAPER CURRENT
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